As elderly populations increase, there is a marked increase in the occurrence of debilitating eye diseases. Common diseases include Advanced Age Related Macular Degeneration, Glaucoma, Diabetic Retinopathy and Cataracts. All of these diseases can lead to severe vision loss and blindness. Macular degeneration is the leading cause of all blindness. The macula is a specialized region in the center of the retina that provides detailed central vision. Macular degeneration typically produces a severe vision loss in the central field of view of an individual.
Technology struggles to provide assistance to advanced stages of disease. External visual aids can provide assistance to patients with severe vision loss. However, external visual aids have restricted functionality. External magnifying glasses and external telescopes provide narrow fields of view. Such external aids also tend to be cumbersome and aesthetically unappealing.
Significant efforts have also been directed toward providing surgical solutions to aid vision in the case of severe vision loss and/or blindness. One approach that has been investigated to address severe vision disabilities is an implantable telescope. U.S. Pat. No. 6,596,026, for example, describes an implantable miniature telescope. Additional variations are described in U.S. Pat. Nos. 5,354,335; 5,391,202; 5,814,103; 5,876,442; 5,928,283; 6,007,579 and 6,066,171. Implantable telescopes can be Galilean and can correct central field defects.
Vision Care Ophthalmic Technologies has produced prototype implantable telescope devices to correct for central field defects. The telescope is referred to the implantable miniature telescope. The implantable miniature telescope is, at the time of filing of this application, currently in the process of clinical studies. The implantable miniature telescope is configured for implantation in the posterior capsular bag, taking the place of the eye's crystalline lens. It consists of two microlenses arranged to magnify, by 2.2× or 2.7× nominal magnification the central visual field of a patient's vision. The is device is a prosthetic telescope and acts in cooperation with the patient's cornea to provide enlarged images. Wide and normal models having 3× or 2.2× (2.7 or 2.2× nominal) magnification have been developed. With the magnification provided by the telescope, images in the central visual field can be focused over other healthy areas of the central and peripheral retina.
The implantable miniature telescope has a number of disadvantages. Initial FDA testing has revealed safety concerns with the implantable telescope. The FDA, in a Jul. 14, 2006 Panel Meeting Summary of the Ophthalmic Devices Panel found that testing of the implantable miniature telescope did not provide reasonable assurance that the device was safe. A major safety concern identified by the panel was endothelial cell density loss.
Problems of the implantable miniature telescope and the likely causes of the problems have been identified and are addressed by the present invention. The surgical solution for the implantable miniature telescope involves a surgical entrance through the side of the eye. This approach is borrowed from cataract surgery, and comes with the problems associated with cataract surgery.
A haptic ring mounts the device in a capsular bag placement. This position may shift with time, causing problems with maintaining central position of the device. Central position is critical to maintaining the beneficial effect of the telescope, and stability is critical to maintaining healthy tissue. Additionally, the position relative to the cornea is not stable and movement toward the cornea can cause injury to endothelial cells and lead to corneal decompensation. Damage caused to the cornea is contradictory to the necessary eye condition to obtain benefit of the telescope. Implantation is not considered even in the clinical studies for patients having levels of cornea opacity, decreased endothelial cell count, or a compromised capsular bag.
The instability in addition to the materials and configuration of the haptic ring may also be the cause of the endothelial tissue losses experienced in clinical studies. The telescope relies upon a transparent cornea, and its application requires a healthy cornea to begin with.
A separate area of research concerns cornea opacities. Cornea issues have been considered separately from the retinal issues. The primary model for cornea repair is donor corneal tissue. For cases of repeated corneal graft rejection, Keratoprosthesis (artificial cornea) devices have been investigated. Examples are disclosed in U.S. Pat. Nos. 4,923,466; 4,586,929; 5,300,116; 5,458,819; 5,843,185; 5,354,332, and 4,470,159. The model for such a device has been the replacement of the diseased cornea with an artificial one. Several devices have been implanted and studied. Donor corneal tissue remains the favored approach.